When television broadcast and recorded video/audio contents are watched/listened to, an apparatus is used that reproduces sound of these contents. A sound reproducing apparatus is applied to apparatuses etc., having an ability of the sound reproducing apparatus such as television, audio equipment, and PC, for example, and has a function of inputting sound signals of broadcast wave and recorded audio/video contents to output sound from speakers included in these apparatuses or externally connected.
When a user listens to reproduced sound by using such a sound reproducing apparatus, the user normally adjust a sound volume to listen to the sound in accordance with user's preference or necessity. For example, when an elderly person listens to reproduced sound, small sound is difficult to hear due to the weakened auditory function, etc., specific to elderly persons. Since such an elderly person is difficult to hear human voices such as words and vocals included in the reproduced sound as compared to younger persons, it is preferred to provide control so as to emphasize a frequency range including human voice as sound characteristic control for elderly persons.
In this case, if it is attempted to increase a sound volume to accurately hear human voices, noises and sound effects are also increased other than human voices and, therefore, the human voices do not necessarily become easier to hear. If a sound volume is increased, sound may be felt too loud and cause annoyance due to changes in the auditory function specific to elderly persons, as compared to younger persons.
FIG. 14 is a diagram of a state of deterioration in hearing due to aging depicted in a modeled manner. As depicted in FIG. 14, in general, the human auditory function gradually weakens with age and sound of a smaller sound volume becomes difficult to hear. Hearing particularly becomes worse in higher frequency bands, and sounds in higher frequency bands are more difficult to hear than that in lower frequency bands.
Elderly persons feel loud sound louder than younger persons due to an over recruitment phenomenon and may feel annoyance. FIG. 15 is a diagram of an example of how sound is heard due to the over recruitment phenomenon depicted in a modeled manner. As depicted in FIG. 15, in the case of elderly persons, for example, audible sound pressure abruptly rises after exceeding 60 dBSPL, and sound becomes audible at the level of sound pressure same as normal persons (e.g., younger persons) in about 80 dBSPL. After exceeding 80 dBSPL, elderly persons feel sound louder than normal persons. Therefore, such a phenomenon is observed that loud sound is heard louder while small sound is difficult to hear. Although it depends on an individual, such a phenomenon is specific to elderly persons.
Therefore, elderly persons have a problem that human voices such as vocals and words cannot clearly be recognized because sound is difficult to hear at a smaller sound volume and elderly persons also have a problem that a larger sound volume is felt louder than younger persons and adversely causes annoyance even if control is provided to emphasize human voices at a smaller sound volume because how sound is heard changes depending on sound volume.
Therefore, for broadcast wave and contents being reproduced, sound (human voice) must be emphasized to suppress noise and music depending on the situation and, even if a sound volume is increased or decreased on this occasion, output sound characteristics must optimally be controlled to prevent the feeling of annoyance.
For example, Patent Document 1 discloses a vocal sound band emphasis circuit that emphasizes vocal/word such that the vocal/word is clearly heard during a small sound volume and that appropriately emphasizes vocal/word while maintaining a balance of original sound during a medium sound volume or larger. The vocal sound band emphasis circuit includes an in-phase component extracting circuit taking out an in-phase component A from both L/R channel signals, a band pass filter extracting a vocal sound band B from the in-phase component A, a notch filter absorbing and attenuating a prescribed frequency component C from the vocal sound band B, an automatic level control circuit (ALC) amplifying an output signal D and outputting an output signal E, a microcomputer controlling an amplification level, and first and second synthesis circuits synthesizing the output signal E and input L/R channels and outputting them as vocal sound band emphasis L/R channel signals Lout and Rout. The microcomputer determines a signal level and/or a setting volume value of an original audio signal and controls the amplification level of the automatic level control circuit in a substantially inverse proportion relation.